Electric motor driven actuators are used for operation of various components throughout industry. For example, ITT Aerospace Controls, a company related to the assignee of the present invention, manufactures rotary actuators that are identified in commerce as part numbers S343T003-39 or MA20A1001-1 and depicted in FIGS. 1A and 1B. These actuators are typically used in aircraft on ball, butterfly, and/or gate valves on lines that supply, for example, water, hydraulic fluid, and/or fuel.
Actuator 10 utilizes a DC motor 12 and a planetary gear train 14 to provide 90-degree rotary actuation of output shaft 16. Typically, a cam (not shown) attached to output shaft 16 inside housing 24 activates one or more electro-mechanical micro-switches 18 for limitation of travel and indication of position of the actuator. Typically, four micro-switches are provided: two (one at each end) to limit travel and two to indicate position. A relay (not shown) typically controls the direction of the DC motor. Motor 12 is mounted on motor plate 20 and micro-switches 18 are mounted on switch plate 22, all of which are encased in housing 24 having a bottom cover 25. Manual valve handle 26 mounted to the output shaft 16 below the switch plate allows manual activation of the valve and visually indicates the valve position even in the absence of power. A manual stop 23 at each end of travel for the manual valve handle 26 provides a mechanical limit to travel of the output shaft.
There is a need in the art, however, for simplifying the mechanical design, improving reliability, improving manufacturability, and enhancing control of such actuators, while still maintaining a long life in a harsh operating environment, with minimal incremental cost required to make the improvements and enhancements.